Machines for polishing and machines for cleaning wafers and disks in the electronics industry are generally well known. For example, semiconductor wafers, magnetic disks, and other workpieces often come in the form of flat, substantially planar, circular disks. In the manufacture of integrated circuits, semiconductor wafer disks are sliced from a silicon ingot and prepared for further processing. After each wafer is sliced from the ingot, it must be thoroughly polished and then cleaned, rinsed, and dried to remove debris from the surface of the wafer. Thereafter, a series of steps are performed on the wafer to build the integrated circuits on the wafer surface, including applying a layer of microelectronic structures and thereafter applying a dielectric layer. Typically, after the layers are fabricated on the wafer surfaces, the wafers must be planarized to remove excess material and imperfections.
After each processing step, it is often desirable to thoroughly clean, rinse, and dry the wafers to ensure that debris is removed from the wafers. Thus, a method and apparatus for quickly and efficiently cleaning, rinsing, and drying wafers is needed which facilitates high wafer throughput, while at the same time thoroughly cleaning and drying the wafers with a minimum of wafer breakage. For a discussion of existing wafer cleaning machines, see, for example, Lutz, U.S. Pat. No. 5,442,828, issued Aug. 22, 1995; Frank et al., U.S. Pat. No. 5,213,451, issued May 25, 1993; and Onodera, U.S. Pat. No. 5,357,645, issued Oct. 25, 1994.
Presently, CMP polishing and/or planarization is performed by one machine and wafer cleaning and drying is performed by another, separate machine. After a processing layer (i.e., oxide, tungsten or the like) has been deposited on the surface of the wafers, the dry wafers are placed in a cassette and hand carried to a CMP polishing machine. The CMP machine removes excess material by planarizing the wafers, and then typically rinses the wafers and places the wafers into a wet cassette. After polishing, residual particles still reside on the wafer's surface. If these particles dry on the wafer prior to cleaning, the microelectronic structures on the wafer may be corrupted. Therefore, it is extremely important to keep the wafers wet prior to cleaning and drying the wafers. From the CMP machine, the wet cassettes are hand carried to a separate wafer cleaning and drying machine which is typically located somewhere near the CMP machine.
This conventional practice of utilizing separate machines for wafer polishing and for wafer cleaning and drying has serious drawbacks. First, wafer manufacturers must have personnel, equipment and facilities on hand to transport wafers in a wet environment from a CMP machine to a cleaning and drying machine. Secondly, having separate machines for polishing wafers and for cleaning wafers consumes a significant amount of clean room space which, as one skilled in the art will appreciate, is very expensive.